1. Field of the Invention
The present invention relates to a composite material composed of different materials and a resin mold of this composite material used for manufacturing a molding by hardening fluid resin.
2. Description of the Background Art
Transfer molding or injection molding is employed for conventional resin molding. According to this method, fluid resin is charged into a cavity provided in a resin mold. Thereafter the charged fluid resin is hardened to form hardened resin. Consequently, a molding having the hardened resin is formed. In the aforementioned method, releasability between the hardened resin and the surface of the mold must be so improved that the molding can be easily taken out.
For example, an organic material such as polytetrafluoroethylene or silicone rubber having excellent unwettability against the fluid resin is favorable as a surface modification material promoting release between the mold and the hardened resin. In practice, there is proposed a method of coating a mold surface with the organic material by spraying or applying this organic material onto the mold surface (e.g., Japanese Patent Laying-Open No. 7-329099 (1995), pp. 3-4).
In order to seal a chip-type electronic component such as an LSI chip mounted on a lead frame or a printed board with resin, thermosetting resin such as epoxy resin, for example, containing a ceramic filler is used as fluid resin. This ceramic filler wears the surface of the mold, i.e., the mold surface. In order to avoid this wear, a film of a wear-resistant inorganic hard material such as Cr, TiC or CrN, for example is formed on the mold surface. The film of the inorganic hard material is formed by coating the mold surface with the wear-resistant inorganic hard material by plating, PVD (physical vapor deposition) or CVD (chemical vapor deposition).
However, the aforementioned prior art has the following problems:
First, the organic material such as polytetrafluoroethylene or silicone rubber employed for coating the mold surface is easily worn by the ceramic filler contained in the fluid resin. Therefore, it is difficult to singly use this organic material as the surface modification material for the mold.
Second, the wear-resistant inorganic hard material such as Cr, TiC or CrN constituting the film formed on the mold surface is so insufficient in unwettability against the fluid resin that releasability between the fluid resin and the mold surface is insufficient. Further, this inorganic material has a high elastic coefficient, and the difference between the thermal expansion coefficients of the inorganic material and the material for the mold is large. Therefore, remarkable thermal stress is caused on the interface between the film of the inorganic material and the mold surface in a cooling process after formation of the film. Thus, the film of the inorganic material may be separated from the mold surface due to stress repetitively caused during application of the mold.
The present invention has been proposed in consideration of the aforementioned problems, and an object thereof is to improve, in a composite material used for a portion coming into contact with fluid resin, low adhesiveness between the surface of the composite material and hardened resin, more specifically releasability between the resin and a mold surface when the composite material is applied to a resin mold, while improving wear resistance of the composite material against the fluid resin.